644240637 has 6 divisors (see below), whose sum is σ = 930569822. Its totient is φ = 429493752.

The previous prime is 644240591. The next prime is 644240659. The reversal of 644240637 is 736042446.

644240637 is a `hidden beast` number, since 644 + 2 + 4 + 0 + 6 + 3 + 7 = 666.

It can be written as a sum of positive squares in only one way, i.e., 614494521 + 29746116 = 24789^2 + 5454^2 .

It is not a de Polignac number, because 644240637 - 2¹¹ = 644238589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644240837) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35791138 + ... + 35791155.

Almost surely, 2^644240637 is an apocalyptic number.

It is an amenable number.

644240637 is a deficient number, since it is larger than the sum of its proper divisors (286329185).

644240637 is a wasteful number, since it uses less digits than its factorization.

644240637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71582299 (or 71582296 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 36.

The square root of 644240637 is about 25381.8958511771. The cubic root of 644240637 is about 863.6730574007.

The spelling of 644240637 in words is "six hundred forty-four million, two hundred forty thousand, six hundred thirty-seven".